The Science Behind Powder Coating for the Medical Industry

By Troy Newport

Coating for the medical industry requires a level of precision and data collection that many powder coaters don’t have to worry about. But when your parts are used in sterile hospital environments in the vicinity of potentially immunocompromised patients, precision cannot be an accident. Instead, close attention must be paid to science and engineering to stay ahead of the demands of the medical device industry.

President and CEO of Surgical Coatings James Morris literally grew up in the medical device coatings industry. He recently took time out of his busy schedule to talk about his experiences learning about life and the industry from his father.

Your father founded the company you now run, and you essentially grew up in the industry. Tell me some of the things you learned from your father.
I would argue that work ethic, persistence, and integrity are some of the hardest lessons from my youth. I missed fun times with friends and family because of work and responsibilities. When I was about 10 years old, I remember working with my dad all day while we had family in town. We went to work at about 6:30 a.m., and I don’t think we got home until 8:30 or 9:00 p.m. that night. I was exhausted and felt like I missed out on everything I wanted to do that day. I didn’t see the point of working if it meant missing out on all the fun with everyone else. Before I could open the car door, my dad told me he was proud of me and handed me $200 in cash, a small fortune for a 10-year-old. He told me, “What you have in this world, whether it is money or love, is returned by how hard you worked to get it.” He proceeded to give me a $3 per hour raise. What he would say next would shape my attitude toward hard work for the rest of my life. “You shouldn’t mind working if you don’t mind getting paid. Hard work will always pay off, maybe not tomorrow or the next day, but one day you will look back on this and realize that your persistence in a single day caused a chain reaction that made you a millionaire.” I giggled in response, thinking it was another one of his oddly amusing pieces of wisdom.

How did you transition into your current role with the company?
When I was 23 and my father was on his death bed, I got a frantic call from the shop. My dad scheduled a meeting before his health took a quick turn for the worse and they needed me to manage the meeting. I threw on a nice shirt, jumped in the car, and headed for the shop. I had never been in a meeting by myself, much less leading a meeting. I was emotional from the situation and terrified of the unknown. So many questions hit me on that drive to the shop. Was this the beginning of the end for the company? Can anyone at the shop fill my father’s role? Who will support the family now?

When I arrived at the shop, my brain and body went into autopilot. I remember feeling this unusual out-of- body experience, like I was looking down on myself in the meeting. During the shop tour, I used vocabulary and skills I wasn’t aware I even had in my toolbox. As I sat with the two gentlemen in the conference room—one the owner of one of Germany’s largest medical device manufacturers, the other a medical device veteran who recently sold his company to one of the largest medical device companies in the world—I was in shock. But I still had answers to every question they asked.

On my way back home from the meeting, I was overwhelmed and dumbfounded. It all made sense now. All the years of working when I didn’t want to; all the summers I spent in front of a laser or coating parts until 3:00 a.m.; all the weekends building and programming machines; my father had instilled about two decades’ worth of medical device and engineering experience without me knowing it. Weeks later I went to lunch with one of the men who visited that day and learned both men were impressed. That lunch meeting was with Jonathan Thorne, who quickly became a friend, a mentor, and later became my business partner with whom I trust my life.

My father passed away on July 31, 2011. I closed on buying his company on July 31, 2018, seven years later to the day. The persistence he taught me will never go away. The experience of acquiring his company was necessary and painful and keeps me grounded as we push into a new era.

What are some of the biggest changes the medical device industry has seen since you’ve been working in it?
The most important technical changes follow automation and machine design trends. We have always had to employ automation to hit the tolerances and quality necessary for medical devices. In 1998, the company started applying an ETFE (ethylene tetrafluoroethylene) coating to a particular medical device. The coating thickness is controlled at +/-0.003 inches on this device, a challenging specification to achieve in 1998. With the aid of some in-house developed software, substantially better automation, some heavily modified powder coating guns, and post-coating processes, we control the same ETFE coating thickness on a new device to +/- 0.0002 inches. We have consistently pushed the boundary of powder coating controls since the company’s founding. The level of control offered on powder coating equipment does not usually fit our needs out of the box, so we have to modify,adapt, and redesign standard powder coating equipment to fit medical device applications.

Since the company started, we have had a strong background in lasers and optics, which may not seem like a constituent coating process at first glance. In 2000, we started finding several applications that necessitated developing one of our most essential tools, Virtual Masking™. We spent decades engineering and perfecting the laser ablation of coatings from the substrates we coat. With our Virtual Masking™ technology, we remove coatings in very specific and controlled areas achieving otherwise impossible results. It has allowed us to be very efficient when working on single-use devices. We produce medical devices that display masking performance eight times what Six-Sigma qualifications would require. We have Performance Qualifications using our Virtual Masking™ that have recorded process capability index (Cpk) values of 20.88. Statistically, this is zero parts- per-million failing masking specifications and more than ten standard deviations away from minimum or maximum specification limits.

If you brought an experienced powder coater into your facility, what would surprise him/her the most about your processes compared with a ‘standard’ powder coating shop?
Tolerances and control would surprise an experienced coater entering our facility. We have TGIC polyesters controlled to +/-0.0007 inches in coating thickness. Our automated systems measure and log in-process coating thickness in real time in three to five areas using laser micrometers. That data is then captured and sent to our server, logging the SPC data for our customers. We use data collected to calculate the finished and cured coating thickness to automatically segregate parts on the line, before curing. Our system is sophisticated enough to segregate a single part for being too thick, too thin, or because it missed a measurement for any reason. This real-time coating thickness data is used to keep an eye on the PID (proportional–integral–derivative) control software, which automatically adjusts voltage, amperage, powder output, total air volume, correction factors, rinsing air, line speed, and the other 20 variables we constantly log and track on every batch of parts.
 
What application methods do you use? Are there certain types of medical instruments that are generally paired with a specific application process, and why?
We have used liquid, powder, and flame deposition coatings. Using revenue as a reference point, we use electrostatic spray applications for about 82% of applications. We have used flame deposition to apply ceramic coatings in the past, but we have found better-performing materials for those particular medical devices.

Focusing on the electrostatic spray applications, we see many robotic medical devices utilizing powder coating materials. We apply PEEK (polyetheretherketone), fluoropolymers, epoxies, polyesters, hybrid polyolefins, and others with our electrostatic spray applications. Most of the time, it’s not necessarily a particular device type that dictates the powder coating but coating thickness and device specifications that dictate what application we use for certain chemistries. Every medical device is unique and different, and it must be approached as such. If a device needs high dielectric strength at high frequency and abrasion resistance, it is often a good fit for powder coating chemistry and application. In contrast, if a device needs a high dielectric strength at less than 0.002 inches in coating thickness, it will likely be a good fit for liquid coating chemistry and application. Whenever a coating thickness breaks about 0.003 inches, we will try to utilize a powder coating chemistry. Powder coating is a cheaper application than most liquid coatings and inherently has less waste. This translates to cost savings for customers with high-volume single-use devices.

What is the most process-intensive product you coat and why?
The most process-intensive device we coat is a monopolar ablator device. The device uses a TGIC polyester at a 16 mil nominal coating thickness in one area and 22 mil nominal coating thickness in another area of the part. The device starts with an automated process that deposits a bead of biocompatible epoxy adhesive around an electrode area and secures a ceramic isolator to the area surrounding the electrode. The same electrode is then masked with a proprietary masking material to prevent the coating from entering the electrode teeth, which is also an automated process. After the electrode is masked, the part is coated to two different thickness specifications in two different areas. The coating on the device is not trivial, and coating an isolated non-conductive ceramic introduces more challenges. After the device is coated, we use Virtual Masking™ to remove the coating from the substrate in two places. The first being the proximal end which is rudimentary. The second area that is Virtual Masked™ is the perfect circle around the electrode, exposing the ceramic isolator around the electrode. After our Virtual Masking™ processes, the part is quality inspected to very rigorous inspection guidelines, which involve 60X magnification. All in all, there are over 20 routing steps on the part.

Do you work with your powder suppliers on formulation, or do you have your own staff who work on formulation?
We mainly work with powder suppliers for formulations when we do not find a product that will meet a device’s requirements. There is a caveat to working with powder suppliers. We have extensive knowledge of biocompatibility and regulatory constraints on coatings. For example, we know if a coating contains a chemical like BADGE (Bisphenol A diglycidyl ether) and exceeds a certain surface area, it will leach into a patient at a toxic level and never pass EU or FDA regulations. We have established a database of over 300 coatings over the last 25 years. We know what chemistries and coatings work with what types of sterilization, what insulative properties, abrasion, or temperature use properties particular chemistries and formulations will have. We rarely need to formulate a coating with a powder supplier. When we do, it almost always involves direct access to the directors of chemistry or other higher powers.

We also do not like using unnecessary proprietary formulations, and we supply our customers with the coating IDs and the vendors we use so they can mitigate risk in their supply chain and find a second source for the coating applications if necessary.

I’d say plastics, titanium, and magnesium. Titanium and magnesium can be difficult to achieve excellent adhesion without chemical pretreatment in some cases. Magnesium is dangerous when parting lines need to be removed by grinding prior to coating. Plastics are hard to electrostatically powder coat as there is no ground on the part, and the temperature requirements for curing can often limit powder coating chemistries to just a few. Regardless of missing a ground, we apply powder coatings on plastics with exceptional tolerances.

Many products you coat are single use—what average lifespan is expected for reusable instruments?
The average lifespan of a medical device is seven to 10 years. The reusable instruments we coat vary in use from five to 400 sterilization cycles. Some of the coatings we apply can withstand severe abuse in a surgical environment and can be reused several times. How many times a device can be reused is also a function of regulatory requirements and sterilization methods. Our coating often exceeds the requirements or lifespan of other parts of the assembled device.

What are some of the specifications your customers would like to see in the future, and how close is the industry to achieving those specs?
Some of the more demanding specifications we have struggled with have been high dielectric coatings less than 2 mils thick. We have recently identified a group of chemistries and materials that can achieve this specification.

We have also had difficulty replacing a powder coating that needs a high dielectric strength and incredible abrasion resistance with flexibility. The dielectric strength and gloss vary on every single box of powder we receive and leads to some exciting controls we have had to implement to ensure a conforming coating. We have struggled with coating suppliers to find a formulation that would be suitable to replace this particular material. If a power coating supplier is reading this, maybe it brings some much-needed attention to the project. We are currently using over 10,000 pounds of this material a year.

Do you have any expansion plans you can talk about?
We are expanding to provide medical device coating services for Europe and other regions. I hope it affects the medical device coatings industry positively, and more importantly, I hope it can drive medical device innovation in regions that need it most. If we can provide high-quality coating services for other regions, we are helping patients in a small but meaningful way. The EU has always had excellent regulations for patient safety. I expect expanding into this region will help drive some more continuity between the FDA and EU regulatory bodies.

We are also in the process of finding a new facility to move into. We are currently in a 7,000 square foot facility, and we are looking for about 16,000 square feet as we expand. Aside from the move, we are taking the opportunity to design and build our next-generation Virtual Masking™ and automated coating lines. Several stages of automated parts handling will be added on our powder coating lines and Virtual Masking™ systems. The next-generation automated coating lines will pick and place parts for our operators. We will continue advancing the technology gap in the coming years, and we enjoy staying at the forefront of powder coating and masking technologies for the medical device industry.

Troy Newport is publisher, Powder Coated Tough